Add `r'/`l' grep command history commands

* doc/emacs/building.texi (Grep Searching): Mention the
`r'/`l' commands.

* lisp/progmodes/grep.el (grep-forward-history): New command.
(grep-backward-history): Ditto.
(grep--save-buffers): New function.
(grep): Use it to record the history.
(grep--command-history, grep--history-inhibit)
(grep--history-place): New internal variables for the grep
history (bug#22627).

1 files changed, 5 insertions, 0 deletions

diff --git a/etc/NEWS b/etc/NEWS
index d878228720e..88e101ee0f0 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -57,6 +57,10 @@ has been added.  They are: 'file-attribute-type',
 ** The new function 'buffer-hash' has been added, and can be used to
 compute a fash, non-consing hash of the contents of a buffer.
 
++++
+** The grep mode now has a command history that you can access via the
+`r' and `l' commands.
+
 ---
 ** 'fill-paragraph' no longer marks the buffer as changed unless it
 actually changed something.
@@ -1807,6 +1811,7 @@ behavior, set 'diff-switches' to '-c'.
 dynamically.  Any third-party code that changes these templates should
 be updated accordingly.
 
++++
 ** The grep/rgrep/lgrep functions will now ask about saving files
 before running.  This is controlled by the 'grep-save-buffers'
 variable.